The present invention relates to the measurement of optical characteristics of components, and more particularly to a single sweep polarization dependent loss (PDL) measurement method and apparatus using a swept-wavelength system.
There currently are basically three approaches for measuring the PDL of a passive optical component.                Use four well-known states of polarization at the input of the optical component, sweep a range of wavelengths for each state of polarization, and measure the transmitted optical power through the component over each sweep. This is known as the Mueller matrix method and is described in U.S. Pat. No. 5,371,597.        Use three well-known states of polarizaton at the input of the optical component, sweep a range of wavelengths for each state of polarization, and measure the Jones vector of the light that is transmitted through the component for each sweep. This is known as the Jones matrix method and is described in U.S. Pat. Nos. 5,298,972 and 5,227,623.        Use random states of polarization at the input of the optical component and measure the transmitted optical power for each random state. This is a well-known method that is described in Fiber Optic Test and Measurement by Dennis Derickson, page 354, published Oct. 8, 1997 by Prentice Hall. Mathematical algorithms are then applied to these data to determine the PDL —see for example TIA/EIA FOTP-157, Measurement of Polarization-Dependent Loss (PDL) of Single-Mode Fiber Optic Components.        
Each of these techniques require multiple measurements taken in sequence, i.e., in sequential sweeps, at different states of polarization (SOP).
What is desired is a simple PDL measurement technique that is robust and reduces the measurement time.